1.2 Memory

1.2 Memory

1. RAM

   • RAM is volatile, meaning that all data and information stored in RAM is cleared once the computer is turned off
   • RAM: (Random Access memory) Memory that stores data about the current programs running
   • RAM additionally is the fastest type of memory but it is also the most expensive to buy or upgrade

2. ROM

   • ROM is a type of non-volatile memory, meaning when the computer is powered off all data is retained.
   • ROM: (Read Only Memory) This is data that can only be read. This means it can not be changed or accessed.
   • ROM is extremely hard to hack. This is because the information is only to be read and it cannot be accessed
   • An example of ROM is the computer BIOS
     • BIOS (Basic input/output system) contains the programs to load the hardware.
       • Loads up the start up protocol
   • (POST) Power on self test

3. Cache

   • Is memory that can be accessed quicker than normal RAM.
   • Stores frequently used data and instructions. This allows for quicker access of that information
   • There are 3 different levels of cache.
     • Level 1 cache is extremely fast but relatively small, and is usually embedded in the processor chip (CPU).
     • Level 2 cache is often more capacious than L1; it may be located on the CPU or on a separate chip or coprocessor with a high-speed alternative system bus interconnecting the cache to the CPU, so as not to be slowed by traffic on the main system bus.
     • Level 3 cache is typically specialized memory that works to improve the performance of L1 and L2. It can be significantly slower than L1 or L2, but is usually double the speed of RAM. In the case of multicore processors, each core may have its own dedicated L1 and L2 cache, but share a common L3 cache. When an instruction is referenced in the L3 cache, it is typically elevated to a higher tier cache.

4. Flash Memory

   • Flash memory is a non-volatile memory chip used for storage and for transfering data between a personal computer (PC) and digital devices. It has the ability to be electronically reprogrammed and erased
   • Flash memory is typically found in USB flash drives, MP3 players, digital cameras and solid-state drives.
   • Flash memory is very portable. This is because of their compact nature
   • Flash memory is Non-volatile and is typically faster and more reliable than a hard drive

5. Solid State memory

   • Has no moving parts
   • Often found in mobile devices
   • Smaller than a hard drive
   • Is non-volatile, compact memory

6. Virtual memory

   • Virtual memory is a section of volatile memory created temporarily on the storage drive. It is created when a computer is running many processes at once and RAM is running low.
   • Is much slower than main memory because the processing power is used up through the moving of data
   • Found on the hard disk

7. Disk thrashing

   • When a computer's virtual memory subsystem is in a constant state of paging
     • This causes the computer to crash or severely hinders the performance of the computer